Brain implant smaller than grain of salt developed by Cornell, NTU researchers

SINGAPORE – Neural implants, used to monitor brain activity, often require wired connections or bulky hardware to perform their function.

A new implant, however, has been developed to operate wirelessly, and measures just about 300 microns long and 70 microns wide – smaller than a grain of salt.

Dubbed the microscale optoelectronic tetherless electrode, this implant successfully transmitted brain activity data wirelessly from a living animal for over a year.

In the development led by researchers from Cornell University in New York and Nanyang Technological University (NTU), the electrode is powered by red and infrared laser beams which can pass harmlessly through brain tissue.

The brain’s electrical signals are encoded within tiny pulses of infrared light, which transmit data back to a receiver.

A semiconductor diode made of aluminium gallium arsenide – an alloy commonly used in semiconductors – captures light energy to power the circuit and emits light to transmit the data. This process is supported by a low-noise amplifier, which enhances low-power signals, and an optical encoder, a device that converts motion into digital signals.

The researchers’ findings were published in peer-reviewed scientific journal Nature Electronics on Nov 3.

Assistant Professor Lee Sunwoo, from NTU’s School of Electrical and Electronic Engineering, likened the process of embedding standard neural implants in a brain to inserting a chopstick into tofu, emphasising that using such implants could cause damage to the brain.

The electrode shows that the use of light allows implants to be made at an extremely small scale, reducing the risk of damage to the brain, said Prof Lee, who is one of the study’s authors.

“Your mobile phone has about 10 billion transistors, a lot of complexity and functionality, but then you can’t really shove an iPhone into the brain,” he added.

“So what we’ve done is we used about 300 transistors (in the implant), and they provide enough complexity to provide what’s required for neural recording,” he told The Straits Times.

Prof Lee led the research with Professor Alyosha Molnar, from Cornell University’s School of Electrical and Computer Engineering.

He started working on the technology in 2019 as a postdoctoral associate in Prof Molnar’s laboratory at Cornell before joining NTU in 2023.

Prof Molnar first came up with the idea for the electrode in 2001, though research into the device began only about a decade ago.

Researchers first tested the electrode in lab-grown cell cultures, before trying it on mice, introducing the implant into their barrel cortexes – a region of the brain which processes sensory information from the whiskers of rodents.

The implant was able to successfully record electrical activity from neurons – brain nerve cells – as well as activity at the synapses – the junctions where neurons connect and communicate – for one year. Prof Lee said the mice seemed unaffected, remaining healthy and active throughout the period.

In an article in Cornell Chronicle, the American university’s in-house newspaper, Prof Molnar said the electrode could be used to collect electrical recordings from the brain during magnetic resonance imaging scans, not feasible with current implants.

“As far as we know, this is the smallest neural implant that will measure electrical activity in the brain and then report it out wirelessly,” he added.

The electrode uses pulse position modulation, a technology used in satellite optical communications systems that operates on minimal power consumption to transmit and receive data, he noted.

According to Prof Lee, the technology used in the electrode has potential applications such as detecting seizures in patients before they occur. It could also be used to further clinical research, including monitoring the development of organoids – artificially grown masses of cells or tissue that mimic organs and are derived from stem cells.

Such implants could be inserted under the skin of diabetics to monitor their glucose levels, he noted.

In recent years, research into the application of brain implants for diverse purposes has picked up.

In September, brain implant company Neuralink, founded by billionaire Elon Musk, announced that 12 people were using its implants. They enable people with cervical spinal cord injuries or amyotrophic lateral sclerosis to control computers using their thoughts.

On Nov 20, it was reported that the US Food and Drug Administration approved a long-term clinical trial of a brain-computer interface developed by neurotechnology firm Paradromics.

Beginning in early 2026, the trial will see Paradromics’ device implanted in the brains of two volunteers – who are unable to speak because of neurological diseases and injuries – to test its safety and potential to restore their ability to speak.